With ever tightening VOC regulations for consumer insecticides, formulators are being pushed to use more water and/or more LVP (low vapor pressure) fluids that are not reportable as VOCs in their products. The particular choice of LVP fluid and its concentration may also affect the biological performance of insecticide formulations. To demonstrate these effects, a variety of hydrocarbon LVP carrier fluids were combined with the insecticides S-bioallethrin and deltamethrin in both solvent and water-based insecticide formulations. Experiments were conducted to evaluate knockdown and residual activity against German cockroaches.
Data indicated that use of hydrocarbon LVP carrier fluids with higher levels of normal paraffins resulted in faster knockdown of the cockroaches under a variety of test conditions. Higher concentrations of hydrocarbon LVP carrier fluids in water-based formulations also enhanced their knockdown performance. The residual activities of water-based formulations, inferred from the lengths of time the formulations remained efficacious after they were applied to ceramic tile and painted plywood, were adversely affected by higher concentrations of normal paraffins or LVP hydrocarbons.
The results suggest that normal paraffins and higher concentrations of LVP hydrocarbon fluids may increase the penetration of the formulations into insect and household surfaces. With the insects this leads to faster intake of insecticide. With the household surfaces this reduces insecticide availability. One can use this information to select active ingredients, LVP fluids, and their concentrations, along with other formulants, to optimize formulation performance for specific application requirements and meet VOC regulations. Of the LVP hydrocarbon fluids tested, a mixed aliphatic fluid with a moderate concentration (20% w/w) of normal paraffins appeared to offer the best balance of properties for use in crawling insect killers.